SAVE

Available since 1.0.0.

The SAVE commands performs a synchronous save of the dataset producing a
point in time snapshot of all the data inside the Redis instance, in the form
of an RDB file.

You almost never want to call SAVE in production environments where it will
block all the other clients.
Instead usually BGSAVE is used.
However in case of issues preventing Redis to create the background saving child
(for instance errors in the fork(2) system call), the SAVE command can be a
good last resort to perform the dump of the latest dataset.